From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EE9983C819A; Mon, 6 Jul 2026 19:54:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783367685; cv=none; b=B5wLJBw88OLRJM4RleWASqapamV0e6RPmeYpMNRZReX9h2olN0f+Mk18tC7dqAQqUhGIrByMNStmrSLAN3FFFUpUc5V3H6sOYMaYutJsWxzzmzgDxwzHqXh2GhPzem4zvir9mIn5Zov892QE3qxQIAeron7Z8aPsF9I0dPl7SUg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783367685; c=relaxed/simple; bh=r0abEXR+7ZsEZ/d3IqLIGVADmKXy/rJ/hm79XePwdHE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HLwpcCN0uGAZUkZnlCUNMNijcPWAsgm+DHNkc65DoEWVwjW/RnnL2osCgmXX/DZi7ikZWBiXbeLA3/LAS88pOKg1NkGnOn2zGSrDf1HEXpK018tvkFNsOZBlg5oMOsxstTPz6ia2taczpj4wUBDkYq9wMQOGdJoQZIEspfu2x9M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NMQDd1WU; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NMQDd1WU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9C46A1F00A3E; Mon, 6 Jul 2026 19:54:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783367683; bh=txTRsS4azgfOK1sPCmyBxP7wGTwji8FVbplH8c5T1zI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=NMQDd1WUHJLc6ottB4bbTpMgfw2JaZREXzmLT+wgq7KFEfQTOq/BKkBxj0MSyvy5Y qStg+OCIEjCYsJ/5GzGGc8Q64mTBVT+TyeBqwMU11pzdW2d/HosKITMNuj8DxaoUt2 ghFzGSBujycs/95uWAZYDwloCWaX5tSDSozu9iz2+Ml6tenQ9bjjvv/GR0uKbtUJQ/ e/97/3E3Zwq3NVQTlZ4cZy4X738AXzmd/M8qRqQqC6O6IL/oXJPzl/p7KFiCHUqK7D Nim73BYeoSAaPOFWwZCdOGoIFk/C/btBf223lCBO3hc8o1tY/FijwKLtTSGdh0C4ZC ETuEngKEtrz+A== From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: [PATCH v2 3/7] KVM: x86: Disallow EFER.LME and EFER.LMA if long mode is not supported Date: Mon, 6 Jul 2026 19:54:09 +0000 Message-ID: <20260706195413.1966458-4-yosry@kernel.org> X-Mailer: git-send-email 2.55.0.rc2.803.g1fd1e6609c-goog In-Reply-To: <20260706195413.1966458-1-yosry@kernel.org> References: <20260706195413.1966458-1-yosry@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Remove EFER.LME and EFER.LMA from EFER reserved bits only if long mode is actually supported. KVM does check long-mode support before allowing the bits for guest writes and userspace writes through KVM_SET_SREGS* (in __kvm_valid_efer()), but userspace writes through KVM_SET_MSRS only check reserved bits. A nice side effect (and the true motivation) is getting rid of the #ifdeffery when initializing efer_reserved_bits. Signed-off-by: Yosry Ahmed --- arch/x86/kvm/msrs.c | 10 +--------- arch/x86/kvm/x86.c | 3 +++ 2 files changed, 4 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/msrs.c b/arch/x86/kvm/msrs.c index 45170df0ce40b..17d4c813a9e8a 100644 --- a/arch/x86/kvm/msrs.c +++ b/arch/x86/kvm/msrs.c @@ -19,16 +19,8 @@ bool __read_mostly report_ignored_msrs = true; module_param(report_ignored_msrs, bool, 0644); EXPORT_SYMBOL_FOR_KVM_INTERNAL(report_ignored_msrs); -/* EFER defaults: - * - enable syscall per default because its emulated by KVM - * - enable LME and LMA per default on 64 bit KVM - */ -#ifdef CONFIG_X86_64 -static -u64 __read_mostly efer_reserved_bits = ~((u64)(EFER_SCE | EFER_LME | EFER_LMA)); -#else +/* Enable syscall by default because its emulated by KVM */ static u64 __read_mostly efer_reserved_bits = ~((u64)EFER_SCE); -#endif #define MAX_IO_MSRS 256 diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 8dbc0fa302a8b..a0b2c40d93c21 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6892,6 +6892,9 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_setup_xss_caps); static void kvm_setup_efer_caps(void) { + if (kvm_cpu_cap_has(X86_FEATURE_LM)) + kvm_enable_efer_bits(EFER_LME | EFER_LMA); + if (kvm_cpu_cap_has(X86_FEATURE_NX)) kvm_enable_efer_bits(EFER_NX); -- 2.55.0.rc2.803.g1fd1e6609c-goog